| Name | CVE-2026-50257 |
| Description | A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| Debian Bugs | 1138680, 1138703 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| xorg-server (PTS) | bullseye | 2:1.20.11-1+deb11u13 | vulnerable |
| bullseye (security) | 2:1.20.11-1+deb11u17 | vulnerable | |
| bookworm | 2:21.1.7-3+deb12u12 | vulnerable | |
| bookworm (security) | 2:21.1.7-3+deb12u11 | vulnerable | |
| trixie | 2:21.1.16-1.3+deb13u2 | vulnerable | |
| trixie (security) | 2:21.1.16-1.3+deb13u1 | vulnerable | |
| forky, sid | 2:21.1.23-1 | fixed | |
| xwayland (PTS) | bookworm | 2:22.1.9-1 | vulnerable |
| trixie | 2:24.1.6-1 | vulnerable | |
| forky, sid | 2:24.1.12-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| xorg-server | source | (unstable) | 2:21.1.23-1 | 1138680 | ||
| xwayland | source | (unstable) | 2:24.1.12-1 | 1138703 |
[trixie] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)
[bookworm] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)
https://www.openwall.com/lists/oss-security/2026/06/02/1
Fixed by: https://gitlab.freedesktop.org/xorg/xserver/-/commit/f5abfb61994471023d8c6470428c8e30c411cc0b
Fixed by: https://gitlab.freedesktop.org/xorg/xserver/-/commit/f304b57444be3991fd9d3389f309c6eeb056a6c4 (xorg-server-21.1.23)